284 



SCIENCE. 



[Vol. XL No. 2S0 



ous state of the question, except in so far that he has added an- 

 other microbe to the list of the possible specific germs of the dis- 

 ease." 



This would seem to make it very doubtful whether Dr. Gibier of 

 Paris has added any thing to our knowledge of the cause of yellow- 

 fever. 



ELECTRICAL SCIENCE. 

 Novel Current-Registering Instrument. 

 A NEW instrument for measuring the quantity of current sup- 

 plied to consumers has been recently brought out by Prof. Elihu 

 Thomson, although it seems probable that the principle on which 

 it works was originally due to Tavener. Two bulbs are connected 

 by a U-shaped tube, and the whole is partly filled with liquid ; al- 

 cohol, for instance. The arrangement is pivoted, so that, if more 

 of the liquid is forced into one of the bulbs, the difference of weight 

 will cant the apparatus, and its movement is communicated through 

 a ratchet to the hands of a registering-dial. To make this measure 

 the current, two spirals of wire are introduced into the liquid, one 

 in each bulb. If we suppose the instrument has been canted, the 

 spiral in the lower bulb has its circuit made, while that of the upper 

 spiral is broken. The consequence. is, that the liquid in the lower bulb 

 is heated, its vapor-tension increases, and part of it is driven through 

 the U-tube. The section of the latter is very small, so that the liquid 

 passes slowly ;^but;in a time, depending upon this section and on the 

 rate of heating, the upper bulb becomes the heavier, and the apparatus 

 cants, breaking the circuit of the spiral that was previously made, 

 and making the other. By a suitable registering system the read- 

 ings may be made proportional to the current which is flowing. 

 The current, then, is measured by its heating effect, and the instru- 

 ment may be used for both direct and alternating currents. In the 

 latter case the readings would be fairly correct if lamps only were 

 used ; but, if motors were to be run, the readings would not be 

 proportional to the power consumed. This objection holds with all 

 of the instruments that have yet been proposed for the measure- 

 ment of the consumption of alternating currents. 



The Short Series Electric Railway System. — The 

 Short system of electric traction differs from those ordinarily used in 

 that the current is distributed in series, the same current passing 

 through all of the cars on the line. Both overhead and conduit 

 wires are used. In the latter case the wires are contained in an 

 iron conduit, from which they are insulated by porcelain brackets. 

 The overhead wires are supported from iron bracket-poles that 

 arch gracefully over the track. The motors and generators used 

 are of the Brush system. The motor is usually in a front com- 

 partment, and is geared to the front car-a.xle. There is a pinion 

 on the motor-shaft, a gear on the axle, and an intermediate gear 

 and pinion that further reduces the number of revolutions. The 

 gears are made of steel, the pinions of rawhide held between steel 

 plates, making an efficient and noiseless transmitting system. The 

 front compartment (in which the driver stands), with the motor 

 and front truck, can be made separately, and attached to any ordi- 

 nary car by removing the front platform. Taken altogether, the 

 system seems a simple and efficient one. 



An Improvement in Secondary Batteries. — A seem- 

 ingly slight improvement in the construction of secondary batteries, 

 and yet one that in certain cases will be of considerable value, has 

 recently been patented by Mr. J. S. Sellon. A great difficulty and 

 expense in the use of accumulators arises from the fact that the 

 plates cannot be separately and easily removed. Usually, if we 

 wish to connect a number of cells in series, all of the positve plates 

 in each cell are connected together by lead strips, which are taken 

 to similar strips connecting the negative plates of the next cell. 

 The terminals of each plate are burned to the connecting-strip ; 

 and when one of the plates gives out, and we wish to renew it, we 

 must take out the complete set of plates, cut off the one we wish to 

 renew, and solder on another. Besides being difficult, this takes a 

 good deal of time, and increases the cost of maintenance of the 

 battery; it is obvious, too, that it interrupts its use. Mr. Sellon's 

 idea is to have plates made in pairs, a positive and negative, so con- 

 nected that when one of them is in one cell the other will be in an- 

 other. The first and last cells have one set of single plates con- 



nected with the terminals of the external circuit. The advantages 

 of this arrangement are, that plates can be removed and renewed 

 without interfering with the action of the battery, and much more 

 easily than if one of a number of connected plates had to be removed. 

 Any iinprovement in storage-batteries is important at this time, when 

 its advantages, especially for tramway-work, hang in the balance. 

 A slight increase in efficiency will cause their adoption for street- 

 car work, and the invention of Mr. Sellon is in the right direction. 



Influence of Temperature on the Magnetization of 

 Iron. — M. C. Ledeboer has made some interesting experiments 

 on the magnetic properties of iron at high temperatures. Many 

 experiments have been made on the same subject ; and it has been 

 found that up to three or four hundred degrees there is no great 

 change in the magnetic permeability of iron, while at a red heat its 

 magnetic properties almost entirely disappear. The necessary 

 temperature of the iron bar used in the experiment was obtained 

 by a spiral of platinum wire wrapped around it, separated from it 

 by a layer of mica. Between the platinum and the iron was a 

 small thermo-electric couple, which was used to measure the tem- 

 perature of the bar. A heavy electric current sent through the 

 platinum spiral could be regulated to give any desired temperature. 

 The bar used was thick as compared with its length, which fact 

 prevented any useful results as to residual magnetism being ob- 

 tained. M. Ledeboer arrives at the following results : up to a tem- 

 perature of about 680° the magnetic permeability remains nearly 

 constant, after 680° the diminution is very rapid, and the iron ceases 

 to be magnetic at 760". This range of temperature is about that 

 in which several curious phenomena occur, — an abrupt change in 

 the specific heat, a change in the tortional co-efficient, etc.; and it 

 is probable that a more complete study of iron in this region of 

 temperature will help us to connect phenomena which seem now so 

 different in character. 



The Mordey Alternating-Current Dynamo. — This 

 dynamo has revolving magnets and a fixed armature. The latter 

 consists of a number of coils of narrow copper ribbon wound on 

 insulating-cores : they are fixed to project from the inner circum- 

 ference of a metal ring which is fastened firmly to the bed-plate 

 of the dynamo. The magnet consists of a short iron core, whose 

 axis is the axle of the machine, and which is wound with wire sup- 

 plied with current from the small dynamo used as an exciter. 

 From each end of the magnet extend arms, which are bent until 

 they are opposite one another, leaving only enough space between 

 for the flat coils of the armature to pass. We thus have a number 

 of poles of the same sign, opposite to which are poles of the op- 

 posite sign, while between the poles are vacant spaces. The action 

 of the machine is now easily understood : as the magnet revolves, 

 the armature coils are first opposite pole-pieces, where a number 

 of lines of force pass through them ; then in vacant spaces, where 

 there are no lines of force. The variation, of course, produces the 

 electro-motive force of the machine. 



Incandescent Lamps in Explosive Gases. — Lieutenant 

 Hutchins, U.S.N., has been experimenting on the effect of break- 

 ing incandescent lamps in explosive gases. The filament of the 

 lamp breaks almost immediately that the glass is broken, and as 

 soon as it breaks, of course, and cools down, the danger is over. 

 The question was whether the breaking and cooling were so rapid 

 that the gases would not be brought to a sufficiently high tempera- 

 ture to explode. With a Swan l6-candle power lamp, in a mixture 

 of hydrogen and oxygen, the gas exploded immediately the bulb 

 was pierced : the filament was not broken. The same result was 

 obtained with marsh-gas. A Maxim lamp was tried in a mixture 

 of coal-gas and air, with a similar result. Lieutenant Hutchins 

 concludes, that, where explosive gases are allowed to collect on 

 board ship, incandescent electric lights are dangerous. 



BOOK -REVIEWS. 



A Text-Book of Biology. By J. R. AiNSWORTH Davis. Phila- 

 delphia, Blakiston. $4. 



The number of text-books of biology which have been published 

 within recent j'ears has been, it would seem, sufficiently great to 

 meet all reasonable demands ; and yet, after perusing this new one 



